Decaffeination: The CO2 Process
By: Joseph Clark
Background
Caffeine, the world’s most widely consumed psychoactive substance in the world (figure
1). It is a chemical compound that affects the central nervous system as a stimulant,
warding off drowsiness and restoring alertness. The U.S. imports more than 15 million
pounds of caffeine in its pure form of caffeine anhydrous annually. To visualize this, it
would fill 300 40-foot shipping containers, or a train 2 miles long with all the cars filled
with this white powder. Coke and Diet Coke alone require
3.5 million pounds annually to fill the requirement for their
products. Caffeine is naturally occurring in tea, coffee, and
cacao beans, but not all of the caffeine consumed in the
U.S. is natural. There are two main ways in which caffeine
is produced. One method is to synthesize the drug using
fossil fuels as a starting ingredient. The other method is to
decaffeinate coffee or tea and then isolate the compound.
One natural way to produce caffeine is from the
decaffeination of coffee beans. A common method is the
CO2 process, which works through processing coffee beans
with water, carbon dioxide, and heat to extract the caffeine.
This technique works through the hydration of the coffee
The Caffeine Molecule
(Figure 1)
beans, carbon dioxide suffusion, extraction of crude
http://en.wikipedia.org/wiki/Coffee
caffeine, and then refinement of the crude caffeine into
caffeine anhydrous.
In Texas, Maximus Coffee Company is currently processing coffee beans in a facility
roughly the size of 9 Wal-Mart’s. This is the only factory of its kind in the United States
and has been around since the 1980s. The CO2 process is utilized by this facility was
developed by Café Hag and is one of the only large-scale practices, which isolates
chemical-free, natural caffeine. At the Maximus coffee plant they decaffeinate more than
100 million pounds of coffee annually.
The Process: The Maximus Plant
Hydration and CO2 Suffusion
The process begins when the company receives unroasted “green” coffee beans. Coffee
beans naturally occur with roughly a 12% moisture content. The coffee beans are sprayed
with steam and hot water to raise their water content to 35%. Following the hydration of
the coffee beans, they are pneumatically blown to the top of a 280-foot tower. The walls
of the chambers in the tower are 6 inches thick and clad on the inside with stainless steel.
After being shot up into the tower the beans then begin to fall down. As the beans are
falling supercritical carbon dioxide is pumped up through the beans. Due to the
supercritical nature of the CO2, it behaves more like a liquid than a gas. When the CO2
comes into contact with the coffee beans, it passes through them and captures the
caffeine, leaving the coffee beans with the caffeine in tow, the flavor compounds within
the coffee bean intact. The caffeine-laden carbon dioxide is then blended into a column of
water (see figure 2). After being blended into water it flows into a chamber where the
pressure drops from supercritical pressure to normal atmospheric pressure. When the
pressure comes back to normal atmospheric pressure, the caffeine is attracted to the water
as the CO2 evaporates. This carbon dioxide is then captured to be recycled back into the
process. At this point the water and caffeine mixture only contains about one quarter of a
percent of caffeine.
Crude Caffeine Extraction
The water and caffeine mixture now exits the
towers and is pumped toward two 20,000gallon tanks in the back of the facility. From
there, the mixture goes through two
concentrators, where steam coils heat the
solution to evaporate the water, leaving a
highly concentrated liquid. This concentrated
liquid now flows into an arch-toped dryer,
roughly the size of a wood shed. The liquid
looks like hot chocolate syrup at this point as
it flows into the hot rotating drum. During
rotation, the water evaporates, leaving a flaky,
powder residue. A blade then scrapes off this
powder as the drum continues to rotate.
At this point, the powder is only 95% pure and
takes on a tan color. It is poured into plastic
lined cardboard boxes, in which one box holds
one thousand pounds of crude caffeine. Since
the powder is only 95% pure, and contains
roughly 3% water and 2% impurities, it will
need to be processed further to be sold in the
United States as caffeine. There is currently
no company in the U.S. that refines this to
pure caffeine, so this crude caffeine is then
shipped into Mexico to finish the product.
Foreign Refinement
At another facility, in a different country, the
Figure 2
process is completed through sublimation of
http://www.greenerthe crude caffeine into caffeine anhydrous.
industry.org.uk/pages/superCO2/3superCO2_coffee.htm
This process is possible due to the nature of
caffeine possessing a lower boiling point than the impurities that are present in the crude
caffeine. Sublimation of the caffeine starts off by lowering the pressure and temperature
of the compound. First, a zero pressure environment is created by vacuum. Then, ice or a
cooling agent is applied to the product to allow it to become solid. Finally, heat is applied
and the pure caffeine will sublimate from a solid to a gas, before any other solids,
allowing for the capture of pure caffeine.
Conclusion
The CO2 process extracts caffeine from coffee beans using water, heat, and carbon
dioxide. Through the process of bean hydration, carbon dioxide suffusion, crude caffeine
extraction, and refinement of the caffeine, caffeine anhydrous can be isolated. As an allnatural process of gathering caffeine, the CO2 Process is the standard for products that
demand organic or all natural caffeine additives. Since 90% of Americans currently
consume caffeine on a daily basis, this is a process that will be used as long as a demand
for caffeine is continues to exist.
Glossary
1. Pneumatic – Using air pressure to move
2. Supercritical Carbon dioxide – carbon dioxide that is under extreme pressure and
heat at 3500 psi (240 atm) and 190oF
3. Sublimation – To change the state of an element or compound from a solid to a
gas without going through the liquid phase
4. Caffeine Anhydrous – the chemical caffeine in its pure form as a white powder
Sources
1. Carpenter, Murray. Caffeinated: How Our Daily Habit Helps, Hurts, and Hooks
Us. New York City: Penguin Group, 2014. 93-98. Print.
2. "Decaffeination." International Coffee Organization -. International Coffee
Organization, Web. 12 June 2014.